The present invention relates to sensors for sensing electromagnetic conditions. The present invention finds particular application in conjunction with a sensor for sensing the magnitude of magnetic fields. However, the present invention will find other applications including sensing electrical currents by sensing magnetic fields associated therewith, sensing the presence or absence of magnetic fields, the polarity of magnetic fields, and the like.
Heretofore, a variety of electromechanical and electromagnetic field sensors have been utilized to sense magnetic fields. However, such sensors are subject to electrical interference. Electromechanical and electromagnetic sensors which are sensitive to very small magnetic field or magnetic field changes need to be shielded from their own associated electronics. Conversely, the electrical conductors and mechanical mechanisms of the sensors tend to distort the sensed magnetic field.
Fiber optic magnetic field sensors overcome the interference problems of electromechanical and electromagnetic field sensors. One type of fiber optic magnetic field sensor takes advantage of magnetic field dependent polarization properties of certain glasses. Specifically, the polarization of light passing through an optical fiber changes with the strength of the magnetic field. By measuring the amount of rotation of the light polarization, the strength of the magnetic field can be determined. Although these fiber optic magnetic field sensors are more sensitive than electromechanical and electromagnetic sensors and overcome the electrical interference problems, they are significantly more expensive.
The present invention contemplates a new and improved fiber optic sensor that overcomes the above-referenced problems yet is relatively inexpensive to manufacture.